Islam Sk Najmul, Sil Amit, Patra Sanjib K
Department of Chemistry, Indian Institute of Technology Kharagpur, Kharagpur-721302, WB, India.
Dalton Trans. 2017 May 9;46(18):5918-5929. doi: 10.1039/c7dt00895c.
Fluorenyl-alkynyl based π-conjugated rod-shaped oligomers bearing different central aromatic moieties and functionalizable di-alkynyl termini, such as H-[triple bond, length as m-dash]-Fl-[triple bond, length as m-dash]-Fl-[triple bond, length as m-dash]-Fl-[triple bond, length as m-dash]-H (OH1), H-[triple bond, length as m-dash]-Fl-[triple bond, length as m-dash]-Btz-[triple bond, length as m-dash]-Fl-[triple bond, length as m-dash]-H (OH2) and H-[triple bond, length as m-dash]-Fl-[triple bond, length as m-dash]-Btd-[triple bond, length as m-dash]-Fl-[triple bond, length as m-dash]-H (OH3) where Fl = 9,9-dioctylfluorene, Btz = N-hexylbenzotriazole, and Btd = benzothiadiazole, were successfully synthesized by a Pd(0) catalyzed Stille coupling protocol. Electron withdrawing benzothiadiazole and benzotriazole as strong to moderate acceptors and fluorene as the donor have been incorporated to adjust the Donor-Acceptor (D-A) strength for fine-tuning the bandgap (E) as well as the emission wavelength. The corresponding digold(i) σ-complexes (PPh)Au-[triple bond, length as m-dash]-Fl-[triple bond, length as m-dash]-Fl-[triple bond, length as m-dash]-Fl-[triple bond, length as m-dash]-Au(PPh) (OM1), (PPh)Au-[triple bond, length as m-dash]-Fl-[triple bond, length as m-dash]-Btz-[triple bond, length as m-dash]-Fl-[triple bond, length as m-dash]-Au(PPh) (OM2) and (PPh)Au-[triple bond, length as m-dash]-Fl-[triple bond, length as m-dash]-Btd-[triple bond, length as m-dash]-Fl-[triple bond, length as m-dash]-Au(PPh) (OM3) have also been prepared by a reaction of Au(PPh)Cl and methanolic NaOMe in DCM with the corresponding alkynyl functionalized oligomers to take advantage of the heavy-atom effect on their emissive properties. The synthesized rod-shaped π-conjugated fluorene based oligomers and their binuclear Au(i) σ-complexes have been unambiguously characterized by various spectroscopic tools such as FTIR and multinuclear NMR as well as MALDI-TOF and CHN analyses. The absorption and emission spectral studies exhibited a progressive red shift with increasing the electron withdrawing character of the central aromatic unit. The rod-like oligomers having alkynyl termini and the corresponding digold(i) complexes are found to be blue, cyan and yellow emissive, demonstrating the fine-tuning of the emission wavelength. Most importantly, the fluorene based π-conjugated yellow light emitters OH3 and OM3 are successfully achieved by varying the donor/acceptor moiety to the fluorenyl-alkynyl backbone. The digold(i) diacetylide organometallic wires exhibit phosphorescence at 77 K in degassed CHCl due to the efficient intersystem crossing from the S to the T excited state as induced by heavy atoms.
通过钯（0）催化的Stille偶联反应成功合成了基于芴基 - 炔基的π共轭棒状低聚物，这些低聚物带有不同的中心芳族部分和可官能化的二炔基端基，例如H-[三键，长度为m短划线]-Fl-[三键，长度为m短划线]-Fl-[三键，长度为m短划线]-Fl-[三键，长度为m短划线]-H（OH1）、H-[三键，长度为m短划线]-Fl-[三键，长度为m短划线]-Btz-[三键，长度为m短划线]-Fl-[三键，长度为m短划线]-H（OH2）和H-[三键，长度为m短划线]-Fl-[三键，长度为m短划线]-Btd-[三键，长度为m短划线]-Fl-[三键，长度为m短划线]-H（OH3），其中Fl = 9,9 - 二辛基芴，Btz = N - 己基苯并三唑，Btd = 苯并噻二唑。吸电子的苯并噻二唑和苯并三唑作为强到中等的受体以及芴作为供体已被引入，以调节供体 - 受体（D - A）强度，从而微调带隙（E）以及发射波长。相应的二金（I）σ - 配合物（PPh）Au-[三键，长度为m短划线]-Fl-[三键，长度为m短划线]-Fl-[三键，长度为m短划线]-Fl-[三键，长度为m短划线]-Au（PPh）（OM1）、（PPh）Au-[三键，长度为m短划线]-Fl-[三键，长度为m短划线]-Btz-[三键，长度为m短划线]-Fl-[三键，长度为m短划线]-Au（PPh）（OM2）和（PPh）Au-[三键，长度为m短划线]-Fl-[三键，长度为m短划线]-Btd-[三键，长度为m短划线]-Fl-[三键，长度为m短划线]-Au（PPh）（OM3）也通过Au（PPh）Cl与甲醇钠在二氯甲烷中与相应的炔基官能化低聚物反应制备，以利用重原子对其发射性质的影响。合成的基于芴的棒状π共轭低聚物及其双核金（I）配合物已通过各种光谱工具如FTIR、多核NMR以及MALDI - TOF和CHN分析进行了明确表征。吸收和发射光谱研究表明，随着中心芳族单元吸电子特性的增加，出现了逐渐的红移。发现具有炔基端基的棒状低聚物和相应的二金（I）配合物发出蓝色、青色和黄色光，证明了发射波长的微调。最重要的是，通过改变芴基 - 炔基主链上的供体/受体部分，成功实现了基于芴的π共轭黄色发光体OH3和OM3。由于重原子诱导的从S到T激发态的有效系间窜越，二金（I）二乙炔基有机金属线在77 K的脱气氯仿中表现出磷光。
